1. Field of the Invention
This invention relates to prover barrels used in the oil industry for determining the accuracy of flow meters, and more particularly to portable prover barrels.
2. Discussion of the Prior Art
Meters are extensively used in the oil and gas industry to determine flow in order to protect the rights, not only of the seller, but also the buyer of the product flowing through the meters. It is not surprising, therefore, that not only do these meters have to be highly accurate, but they must be "proved" accurate on a regular basis subject to federal and state regulation when dealing with public or on state or federal leases. Prover barrels are extensively used as the instrument to systematically determine the accuracy of such meters. Prover barrels, in turn, must be highly accurate instruments and are checked for accuracy according to standards established by the National Bureau of Standards.
A typical prover barrel consists essentially of flanged, internally phenolic-coated tubular pipe. A series of switches are placed at predetermined locations in the pipe. When a product such as oil moves through the pipe, the oil pushes a sphere ahead of it. The sphere trips a first switch which activates a set of electronic counters, which receive a predetermined number of counts per barrel from the meter. When the sphere activates a second set of switches, the counter stops. Up to four switches can be utilized. The volume of oil between the switches has been previously determined according to measurements performed by standards of the National Bureau of Standards. On the basis of this "proven" volume (and the temperature of the product) the counter readings are utilized to determine the accuracy of the meter. The actual flow through the prover barrel is compared to the reading of the meter and a correction factor is determined. The correction factor is then utilized for every reading of the meter until the next accuracy test.
One example of prior art "prover barrels" that have a fixed situs at the location, are those manufactured by the Smith Meter Systems Division of Geosource, Inc., Erie, Pennsylvania 16512.
An example of a portable prover barrel which is mounted on the flatbed of a truck is that manufactured by Maintenance Mechanical Corp., 3711 Clinton Drive, Houston, Texas. The portable prover barrel is required to determine the accuracy of meters located in the field on a regular periodic basis. A major disadvantage with mounting a prover barrel on the flatbed of a truck is the large amount of "down time" encountered when the truck experiences a mechanical failure. In such cases, valuable contracts may be lost since it is mandatory that regular and systematic inspections of meters be made. Often times, such meters are located in very remote parts of the country where the availability of repair garages is at a minimum. The only feasible solution to this major disadvantage appears in duplicating "prover barrel" flatbed trucks. This alternative, however, is quite costly.
One approach in alleviating the down time of the portable prover barrel is the mounting of the prover barrel on a trailer and the use of a pickup truck or the like for pulling the trailer. If the pickup truck should experience a mechanical failure, the prover barrel can be selectively released therefrom and interconnected with another available pickup truck. This approach also experiences several inherent disadvantages. The trailer requires a heavy-duty bed to accommodate the prover barrel. Such a heavy trailer bed in combination with the weight of the prover barrel results in a considerable wear factor on the truck (increased repair) pulling it to the remote sites which are generally over extremely rough roads and a considerable operating cost in increased gas consumption. Therefore, while the trailer mounted prover barrel has the advantage over the flatbed mounted prover barrel of minimum down time, the flatbed approach offers the advantage of less operating cost and greater ease in arriving at the remote location.
The present invention seeks to obtain the flexibility of a trailer approach (i.e., minimizing the down time problem) and the low weight of the flatbed approach (i.e., minimum operating cost). This is accomplished, under the teachings of the present invention, by arranging the actual tubular elements of the prover barrel in a unique orientation and using the prover barrel itself as the structural components of a trailer. Under the teachings of the present invention, a wheel assembly is mounted to the prover barrel as well as a fifth wheel hook-up.
Another primary disadvantage of the prior art approaches, whether mounted on a flatbed or on a trailer, is the inconvenience of use. The inconvenience in using such prior art approaches becomes clear when it is realized that the proving of the meter must always be witnessed by at least two persons (often more) -- one person represents the buyer of the product and one person represents the seller of the product. In addition to the witnesses, a technician must be on hand to operate the prover barrel. With all of the above portable prior art approaches, these persons experience dramatic environmental conditions since a minimum of five runs is generally necessary to prove the meter, consuming up to several hours at a time in locations that are very remote and at time periods which include the heat of the summer and the blizzard conditions of winter. With all current prior art approaches, the witnesses and the operating technician must operate the prover barrel in such adverse environmental conditions.
Under the teachings of the present invention, the environmental disadvantages are completely overcome by mounting a housing compartment onto the prover barrel. In essence, the prover barrel, under the teachings of the present invention, serves to act as a trailer bed carrying a housing compartment. All controls, thermometers, and other instrumentation are centrally located on the interior of the housing compartment. Prior art approaches simply do not provide for a central location for these components nor for a housing compartment.
As a result, the housing compartment of the present invention provides not only a more comfortable setting for proving and observing the proving of a meter, but a more profitable setting as well. The panel with all the instruments mounted centrally on the interior of the housing provides a greater degree of accuracy in that the instrumentation is protected from the elements. Furthermore, a greater degree of profitability for the owner of the prover barrel is experienced primarily because increased efficiency results in obtaining the readings, especially in adverse environmental conditions. Furthermore, because the technician is not over-tired or over-cold from exposure to the elements, he does a better job for the client.